Chip package and method of forming the same

ABSTRACT

A chip package includes a semiconductor die laterally encapsulating by an insulating encapsulant, a first dielectric portion, conductive vias, conductive traces and a second dielectric portion. The first dielectric portion covers the semiconductor die and the encapsulant. The conductive vias penetrate through the first dielectric portion and electrically connected to the semiconductor die. The conductive traces are disposed on the first dielectric portion. The second dielectric portion is disposed on the first dielectric portion and covering the conductive traces, wherein a first minimum lateral width of a conductive trace among the conductive traces is smaller than a second minimum lateral width of a conductive via among the conductive vias. A method of forming the chip package is also provided.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation application of and claims the priority benefit of a prior Application Ser. No. 17/730,213, filed on Apr. 27, 2022 and now allowed. The Application Ser. No. 17/730,213 is a continuation application of and claims the priority benefit of a prior Application Ser. No. 16/164,752, filed on Oct. 18, 2018, now US Pat. No. 11,322,450 B2. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of this specification.

BACKGROUND

The semiconductor industry has experienced rapid growth due to continuous improvements in the integration density of various electronic components (i.e., transistors, diodes, resistors, capacitors, etc.). For the most part, this improvement in integration density has come from repeated reductions in minimum feature size, which allows more components to be integrated into a given area. With the growing demand for miniaturization, higher speed, greater bandwidth and lower power consumption, there is a need for smaller and more creative packaging for semiconductor dies.

Currently, integrated fan-out packages are becoming increasingly popular for their compactness. In the integrated fan-out packages, the formation of the redistribution circuit structure plays an important role during packaging process. It is important to increase process window and, at the same time, to reduce minimum feature size of the redistribution circuit structure.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the following detailed description when read with the accompanying figures. It is noted that, in accordance with the standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion.

FIGS. 1 through 17 illustrate cross-sectional views of various processing steps during formation of a chip package in accordance with some embodiments.

FIG. 18 illustrates cross-sectional view of a chip package in accordance with some embodiments.

FIGS. 19 through 29 illustrate cross-sectional views of various processing steps during formation of a redistribution structure in accordance with some other embodiments.

FIGS. 30 through 35 illustrate cross-sectional views of various processing steps during formation of a redistribution structure in accordance with some other embodiments.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, or examples, for implementing different features of the provided subject matter. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. For example, the formation of a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed between the first and second features, such that the first and second features may not be in direct contact. In addition, the present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,” “above,” “upper” and the like, may be used herein for ease of description to describe one element or feature’s relationship to another element(s) or feature(s) as illustrated in the figures. The spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The apparatus may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein may likewise be interpreted accordingly.

Other features and processes may also be included. For example, testing structures may be included to aid in the verification testing of the 3D packaging or 3DIC devices. The testing structures may include, for example, test pads formed in a redistribution layer or on a substrate that allows the testing of the 3D packaging or 3DIC, the use of probes and/or probe cards, and the like. The verification testing may be performed on intermediate structures as well as the final structure. Additionally, the structures and methods disclosed herein may be used in conjunction with testing methodologies that incorporate intermediate verification of known good dies to increase the yield and decrease costs.

FIGS. 1 through 17 illustrate cross-sectional views of various processing steps during formation of a chip package in accordance with some embodiments. A single package region is illustrated in FIGS. 1 through 17 , but multiple package regions may be packaged simultaneously, constituting a wafer level packaging process.

Referring to FIG. 1 , a carrier 100 having a de-bonding layer DB, a dielectric layer 104 and a seed layer SL1 formed thereon is provided. The de-bonding layer DB is first formed on the carrier 100, then the dielectric layer 104 is formed on the de-bonding layer DB. In some embodiments, the carrier 100 is a glass substrate, the de-bonding layer DB is a light-to-heat conversion (LTHC) release layer formed on the glass substrate, and the dielectric layer 100 is a photosensitive polybenzoxazole (PBO) layer. In alternative embodiments, the carrier 100 may be a ceramic substrate, the de-bonding layer DB may be a photo-curable release film whose viscosity is decreased by a subsequently performed photo-curing process or a thermal curable release film whose viscosity is decreased by a subsequently performed thermal-curing process, and the dielectric layer 104 may be made from other photosensitive or non-photosensitive dielectric materials.

After forming the dielectric layer 104, a seed layer SL1 is formed over the dielectric layer 104. The seed layer SL1 may be formed using, for example, physical vapor deposition (PVD) or the like. The PVD may be sputtering. In some embodiments, the seed layer SL1 is a metal layer, which may be a single layer or a composite layer comprising sub-layers formed of different materials. In some embodiments, the seed layer SL1 includes a titanium layer and a copper layer over the titanium layer.

Referring to FIG. 2 , after the carrier 100 having the de-bonding layer DB, the dielectric layer 104 and the seed layer SL1 formed thereon is provided, a photoresist PR1 is then formed and patterned on the seed layer SL1. The photoresist PR1 may be formed by spin coating or the like and may be patterned by photolithography to form openings through the photoresist PR1 such that portions of the seed layer SL1 are exposed by the openings in the photoresist PR1.

A conductive material is then formed in the openings of the photoresist PR1 and on the exposed portions of the seed layer SL1 such that a plurality of conductive pillars TV are formed on the seed layer SL1. The conductive material may be formed by plating, such as electroplating, electroless plating, or the like. The conductive material may be a metal such as copper, titanium, tungsten, aluminum, or the like. The photoresist PR1 is removed, and then portions of the seed layer SL1 which are not covered by the conductive pillars TV are removed as shown in FIG. 3 . In some embodiments, the photoresist PR1 may be removed by any acceptable process, such as by an ashing process, a stripping process, or the like. After the photoresist PR1 is removed, the exposed portions of the seed layer SL1 may then be removed by any acceptable process. In some embodiments, the seed layer SL1 may be partially removed by etching process such as wet etching, dry etching, or the like.

Referring to FIG. 4 , semiconductor dies or devices 110 and 120 are then mounted on the dielectric layer 104 and may be surrounded by the conductive pillars TV. In some embodiments, the semiconductor dies 110 and 120 are adhered to the dielectric layer 104 through a die-attach film (DAF) (not shown). The semiconductor die 110 may be a logic die (e.g. central processing units, microcontrollers, etc) while the semiconductor die 120 may be a memory die (e.g. high bandwidth memory (HBM) die, dynamic random access memory (DRAM) die, static random access memory (SRAM) die etc.). In some embodiment, the semiconductor die 120 may be a graphical processing unit (GPU) die. In some embodiments, semiconductor dies 110 and 120 may be power management dies (e.g., power management integrated circuit (PMIC) dies), radio frequency (RF) dies, sensor dies, micro-electro-mechanical-system (MEMS) dies, signal processing dies (e.g., digital signal processing (DSP) dies), front-end dies (e.g., analog front-end (AFE) dies), the like, or a combination thereof. The number of semiconductor dies provided on the dielectric layer is not limited to two. In some embodiments, only semiconductor die 110 or semiconductor die 120 is provided on dielectric layer 104. In some alternative embodiments, other semiconductor dies may be provided on dielectric layer 104 in addition to semiconductor dies 110 and 120.

The semiconductor dies 110 and 120 each includes an active surface having a plurality of die connectors 114 and 124 thereon (illustrated as only one for simplicity) respectively. In the semiconductor die 110, a dielectric layer 112 laterally encapsulates the die connectors 114, side surfaces of the die connectors 114 are in contact with the dielectric layer 112, and top surfaces of the die connectors 114 are exposed through the dielectric layer 112. In some alternative embodiments, the die connector 114 may be covered by and encapsulated in the dielectric layer 112. In the semiconductor die 120, the die connectors 124 are not encapsulated within a dielectric layer and therefore side surfaces and top surfaces of the die connectors 124 are exposed. In some embodiments, the semiconductor die 120 may include a dielectric layer that partially or fully encapsulates die connectors 124. The conductive pillars TV, semiconductor die 110 and semiconductor die 120 may have different dimension along the vertical direction (i.e. different height).

After the semiconductor dies 110 and 120 are mounted on the dielectric layer 104, an insulating encapsulant MC are formed to cover the dielectric layer 104, the semiconductor dies 110 and 120 and the conductive pillars TV. The insulating encapsulant MC may be a molding compound, epoxy, or the like, and may be applied by a molding process (e.g. compression molding, transfer molding, or the like). The insulating encapsulant MC is applied to a level covering the top surfaces of the conductive pillars TV and the semiconductor dies 110 and 120.

Referring to FIG. 5 , the insulating encapsulant MC are partially removed to expose the top surfaces of the conductive pillars TV, the die connectors 114 and the die connectors 124. Preferably, after partially removing the insulating encapsulant MC, the top surface of the remaining insulating encapsulant MC is substantially leveled with the exposed top surfaces of the conductive pillars TV, the die connectors 114 and the die connectors 124. The partial removal of the insulating encapsulant MC may be performed by a grinding process and/or a planarization process such as a chemical mechanical polishing (CMP) process.

Referring to FIGS. 6 through 11 , after partially removing the insulating encapsulant MC, a redistribution layer (RDL) 130 is formed over the semiconductor dies 110 and 120, the conductive pillars TV and the insulating encapsulant MC. As illustrated in FIG. 11 , the RDL 130 includes a dielectric portion 130 a, a dielectric portion 130 b, conductive features 138 a and conductive features 138 b. Conductive features 138 a and conductive features 138 b are referred to as redistribution lines. In some embodiments, conductive features 138 a and conductive features 138 b are formed by a damascene process, described in detail below with reference to FIGS. 6 through 9 . In some embodiments, the RDL 130 is a fine pitch RDL having critical dimension less than 1.0 µm.

In FIG. 6 , dielectric portion 130 a is provided on the semiconductor dies 110 and 120, the conductive pillars TV and the insulating encapsulant MC. The dielectric portion 130 a is then patterned to form via openings 132 exposing conductive pillars TV and semiconductor dies 110 and 120. The via openings 132 may be formed to have a tapered shape in the cross-sectional view. The via openings 132 may be tapered to have a smaller diameter near the conductive pillar TV.

In detail, the dielectric portion 130 a is first evenly deposited, then a photolithography process is performed to pattern the dielectric portion 130 a, and then a curing process is performed on the patterned dielectric portion 130 a. In some embodiments, the even deposition of dielectric portion 130 a provide a top surface that is substantially level or planar, which may be desirable in subsequent fabrication processes. In some embodiment, an additional planarization process such as CMP may be performed on the dielectric portion 130 a before or after the patterning process. In some embodiments, the dielectric portion 130 a is formed of a polymer, which may be a photosensitive material such as PBO, polyimide, benzocyclobutene (BCB), or the like, that may be patterned using photolithography process. In some embodiments, the dielectric portion 130 a may be formed by any acceptable deposition process, such as spin coating, chemical vapor deposition (CVD), laminating, the like, or a combination thereof. After the dielectric portion 130 a is patterned and leaving behind a substantially level or planar top surface, the dielectric portion 130 a may have a thickness T1 of between about 0.2 µm to about 5.0 µm.

Referring to FIG. 7 , a seed layer SL2 is formed on the patterned dielectric portion 130 a and the exposed portions of the conductive pillar TV and the semiconductor dies 110 and 120. That is, the seed layer SL2 is formed on the dielectric portion 130 a conformal to the shape of the via openings 132. The seed layer SL2 may be formed using, for example, PVD or the like. The PVD may be sputtering. In some embodiments, the seed layer SL2 is a metal layer, which may be a single layer or a composite layer comprising sub-layers formed of different materials. In some embodiments, the seed layer SL2 includes a titanium layer and a copper layer over the titanium layer.

Referring to FIG. 8 , after the seed layer SL2 is formed, a photoresist PR2 is then formed over the seed layer SL2 and patterned. The photoresist PR2 is patterned to form a plurality of trenches above the via openings 132 which defines the conductive features formed therein in later processes. Details of the conductive features will be described below. The photoresist PR2 may be patterned by photolithography to form plurality of trenches through the photoresist PR2 such that portions of the seed layer SL2 are exposed by the trenches in the photoresist PR2. The plurality of trenches includes openings 134 a formed directly over and exposing the via openings 132, and trenches 134 b exposing seed layer SL2 in communicating to the openings 134 a. As illustrated in the cross-sectional view of FIG. 8 , the trenches 134 b are formed adjacent to the openings 134 a. In some embodiments, the openings 134 a and the trenches 134 b are not tapered.

Referring to FIG. 9 , after the photoresist PR2 is formed and patterned, a conductive material is then formed in the openings 134 a and trenches 134 b of the photoresist PR2 and on the exposed portions of the seed layer SL2 such that conductive features 138 a and conductive features 138 b are formed on the seed layer SL2. The conductive material may be formed by plating, such as electroplating, electroless plating, or the like. The conductive material may be a metal such as copper, titanium, tungsten, aluminum, or the like. The photoresist PR2 is removed, and then portions of the seed layer SL2 which are not covered by the conductive features 138 a and 138 b are removed. In some embodiments, the photoresist PR2 may be removed by any acceptable process, such as by an ashing process, a stripping process, or the like. After the photoresist PR2 is removed, the exposed portion of the seed layer SL2 may then be removed by any acceptable process. In some embodiments, the seed layer SL2 may be partially removed by etching process such as wet etching, dry etching, or the like.

Still referring to FIG. 9 , the conductive features 138 a refer to the portion of conductive material embedded in the dielectric portion 130 a. That is, the conductive features 138 a are conductive vias which electrically connect the conductive pillar TV and the semiconductor dies 110 and 120 to the conductive features 138 b disposed above the conductive features 138 a. The conductive features 138 b refer to conductive features that lies between the top surface of the dielectric portion 130 a and the top surface of the dielectric portion 130 b (as will be discussed later). In a top view (not shown), the conductive features 138 b may be illustrated as fine pitched conductive traces that extends along the surface of the dielectric portion 130 a for increased routing density.

The conductive features 138 a may have a largest lateral width W1 of between about 1.0 µm to about 5.0 µm. The conductive features 138 b may have a lateral width (also referred to as line width) W2 of between about 0.2 µm to about 0.9 µm. In some embodiments, the critical dimension of the conductive features 138 b is smaller than the critical dimension of the conductive features 138 a. In some embodiment, the critical dimension refers to the minimum lateral width of one conductive feature among plurality of conductive features. In some embodiments, the critical dimension of the conductive features 138 a may be between about 1.0 µm to about 5.0 µm. In some embodiments, the critical dimension of the conductive features 138 b may be between about 0.2 µm to about 0.9 µm.

Referring to FIGS. 10 and 11 , a dielectric portion 130 b is formed over the dielectric portion 130 a covering the entirety of the conductive features 138 b. Due to the topography of conductive features 138 b, the dielectric portion 130 b formed thereon has a surface with low degree of planarization (DOP). That is, the dielectric portion 130 b may have a plurality of protruding features corresponding to the conductive features 138 b disposed thereunder. The dielectric portion 130 b with a top surface of low DOP is shown in FIG. 10 . DOP is a measure of topography of a surface. Higher DOP indicates a surface is more planar, whereas low DOP indicates an uneven surface. Here, the DOP is evaluated using the equation

$\text{DOP} = \left( {1 - \frac{t_{s}}{t}} \right) \times 100\%,$

wherein t_(s) is the height of the protruding feature and t is the height of the feature underlying the protruding feature. The height of the protruding feature is measured from the base of the incline of the protruding feature vertically upwards to the peak level of the protruding feature. In some embodiment, the DOP of dielectric portion 130 b formed covering the conductive features 138 b may be between about 48% and about 100%. In some embodiment, the dielectric portion 130 b is formed of a same material as the dielectric portion 130 a. In some embodiment, the dielectric portion 130 b may be a polymer, which may be a photosensitive material such as PBO, polyimide, benzocyclobutene (BCB), or the like. In some embodiment, the dielectric portion 130 b may be formed from a non-photosensitive material. The dielectric portion 130 b may be formed by spin coating, lamination, chemical vapor deposition (CVD), the like, or a combination thereof.

In FIG. 11 , the uneven top surface of the dielectric portion 130 b is planarized to expose top surfaces of the conductive features 138 b and achieve a high DOP of between about 90% to about 100%. That is, after planarizing the dielectric portion 130 b, the top surface of dielectric portion 130 b and the top surface of the conductive features 138 b is substantially coplanar. The dielectric portion 130 b may have a thickness T2 after the planarization process. In some embodiments, thickness T2 may be between about 0.2 µm to about 0.9 µm.

FIG. 12 illustrates the formation of additional RDL over the first RDL 130. The additional RDL includes dielectric portion 140, conductive features 148 a and conductive features 148 b. The materials used and the process of forming the additional RDL may be the same as the process of forming RDL 130 illustrated in FIGS. 6 through 9 .

In some embodiments, the additional RDL is a fine pitch RDL for high density routing having critical dimensions similar to the RDL 130. In other words, the dielectric portion 140 may be similar to dielectric portion 130 a, the conductive features 148 a may be conductive vias that is similar to conductive features 138 a, and the conductive features 148 b may be redistribution lines formed above conductive features 148 a that is similar to conductive features 138 b. Details of which are not repeated herein. In some embodiments, the materials used to form the additional RDL may be different from the RDL 130. In an alternative embodiment, the formation of the additional RDL including the dielectric portion 140, the conductive features 148 b and 148 b shown in FIG. 12 is omitted. That is, only one fine pitch RDL 130 is formed. In some other embodiment, more than one additional fine pith RDL is formed on the RDL 130. That is, the processes of FIGS. 6 through 11 may be repeatedly performed on RDL 130.

Due to the planarization of dielectric portion 130 b and conductive features 138 a and 138 b, a surface with high DOP is provided for additional fine pitch RDL to be formed thereon. The high DOP allows the additional fine pitch RDL to be formed with larger process window, thus increasing the yield rate of fine pitch packaging process. That is, due to the dielectric portion 130 b having good surface planarity, the dielectric portion 140 may be formed with high DOP thereon. Subsequent patterning (i.e. photolithography) process performed thereon may have good resolution, and fine pitch redistribution layer may be achieved.

Referring to FIGS. 13 through 14 , after forming the additional redistribution layer with the dielectric portion 140, conductive features 148 a and the conductive features 148 b as shown in FIG. 12 , a large scaled redistribution layer including dielectric portion 150 and conductive features 154 are formed thereon. The large scaled redistribution may have critical dimension between about 1 µm to about 50 µm.

In FIG. 13 , dielectric portion 150 is formed covering the entirety of conductive features 148 b and patterned to expose some of the conductive features 148 b. In some embodiment, the dielectric portion 150 may be formed of a photosensitive dielectric material. The dielectric portion 150 may be formed with greater thickness and patterned with wider opening. Despite the topography of the conductive features 148 b, due to the relatively greater thickness of the dielectric portion 150, a relatively high DOP may still be maintained. Moreover, because dielectric portion 150 does not correspond to a fine pitch redistribution layer, the patterning of dielectric portion 150 have a larger process window and planarization maybe omitted.

Referring to FIG. 14 , conductive features 154 are formed in the patterned openings of the dielectric portion 150 and on the top surface of the dielectric portion 150. In some embodiment, a seed layer is first formed conformal to the patterned dielectric portion 150, and photoresist is then formed on the seed layer and subsequently patterned to form openings exposing part of the seed layer. Conductive materials are then plated in the openings of the photoresist layer and on the exposed seed layer to form the conductive features 154. Here, the conductive features 154 collectively refer to the conductive features which connects conductive feature 148 b to the top surface of the dielectric portion 150 and conductive features which is above the dielectric portion 150 which performs redistribution function. The process of forming conductive features 154 may be similar to the process of forming the conductive features 138 a and the conductive features 138 b discussed above with reference to FIGS. 7 to 9 .

In FIG. 15 , a dielectric portion 160, under-ball metallurgies (UBM) 162 and conductive connectors 164 are formed. In detail, the dielectric portion 160 is formed on the dielectric portion 150 and covering the conductive features 154. In some embodiments, the dielectric portion 160 is a photosensitive dielectric material. The dielectric portion 160 is then patterned to form openings exposing conductive features 154. Conductive material is then plated in the openings to form the UBMs 162. The process of forming UBMs 162 may be similar to the process of forming the conductive features 138 a and the conductive features 138 b discussed above with reference to FIGS. 7 to 9 .

After forming UBMs 162, conductive connectors 164 are then formed on the UBMs 162. In some embodiments, the conductive connectors 164 may be ball grid array (BGA) connectors, solder balls, metal pillars, controlled collapse chip connection (C4) bumps, micro bumps, or the like. The conductive connectors 164 may include conductive materials such as solder, copper, aluminum, gold, nickel, silver, palladium, tin, or the like, or the combination thereof. In some embodiments, the conductive connectors may be formed by initially forming a layer of solder on the UBMs 162 followed by a reflow process. After forming the conductive connectors 164, a package 200 with front side redistribution structure is accomplished.

Next, referring to FIG. 16 , after the conductive connectors 164 are formed, the dielectric layer 104 is de-bonded from the de-bonding layer DB such that the dielectric layer 104 is separated or delaminated from the de-bonding layer DB and the carrier 100. In some embodiments, the de-bonding layer DB (e.g., the LTHC release layer) may be irradiated by an UV laser or other suitable photo curing process such that the dielectric layer 104 is peeled from the de-bonding layer DB and the carrier 100. In some alternative embodiments, the de-bonding layer DB may be treated by an acceptable thermal curing process such that the dielectric layer 104 is peeled from the de-bonding layer DB and the carrier 100.

After the de-bonding process, a plurality of packages 200 in wafer form is flipped and placed on a carrier tape 170. The dielectric layer 104 is then patterned to form opening 172 exposing the seed layer SL1 on the conductive pillar TV. In some embodiments, the dielectric layer 104 may be a photosensitive dielectric material and the patterning is performed by photolithography process.

Referring to FIG. 17 , a bonding of package 300 to package 200 is illustrated, thus forming a Package-on-Package (PoP) structure. The bonding is performed through connectors 174, which physically and electrically connects conductive pillars TV to metal pads 302 in the overlying package 300. Connectors 174 connects to the conductive pillar TV through opening 172. In some embodiments, package 300 includes semiconductor dies which may be memory dies such as SRAM dies, DRAM dies, or the like.

In FIG. 18 , an underfill UF is formed in the gap between packages 200 and the overlying packages 300, and is cured. The underfill UF may be a polymer, an epoxy, a resin or the like. After the underfill UF is disposed and cured, a singulation process is performed to separate the plurality of packages 200 and packages 300 in wafer form into a plurality of individual packages 400 each having at least one package 200 and at least one package 300.

FIGS. 19 through 29 illustrate cross-sectional views of various processing steps during formation of a redistribution structure in accordance with some other embodiments. A single package region is illustrated in FIGS. 19 through 29 , but multiple package regions may be packaged simultaneously, constituting a wafer level packaging process.

Referring to FIGS. 19 through 24 , a RDL 230 is formed over the semiconductor dies 110 and 120, the conductive pillars TV and the insulating encapsulant MC. As illustrated in FIG. 24 , the RDL 230 includes a dielectric portion 230 a, a dielectric portion 230 b, conductive features 238 a and conductive features 238 b. Conductive features 238 a and conductive features 238 b are referred to as redistribution lines. In some embodiments, conductive features 238 a and conductive features 238 b are formed by a damascene process, described in detail below. In some embodiments, the RDL 230 is a fine pitch RDL having critical dimension less than 1.0 µm.

Referring to FIG. 19 , a package structure similar to FIG. 5 is provided. In FIG. 19 , a patterned dielectric portion 230 a is provided over the semiconductor dies 110 and 120, the conductive pillars TV and the insulating encapsulant MC. In some embodiments, the dielectric portion 230 a is formed with a thickness T1 similar to the dielectric portion 130 a. The dielectric portion 230 a is patterned to form openings 243 exposing the conductive pillars TV, the semiconductor dies 110 and the semiconductor dies 120. The formation and patterning of dielectric portion 230 a may be similar to dielectric portion 130 a as discussed above with reference to FIG. 6 . Details of which are not repeated.

Referring to FIG. 20 , a dielectric portion 230 b is deposited into the openings 234 and over the dielectric portion 230 a. The dielectric portion 230 b is formed of a positive tone photosensitive dielectric material such as PBO, polyimide, BCB, phenolic, acrylate, phenolic-epoxy hybrid, or the like. The dielectric portion 230 b may be formed by any acceptable deposition process, such as spin coating, chemical vapor deposition (CVD), laminating, the like, or a combination thereof. The use of positive tone photosensitive dielectric material allows openings with smaller dimension to be formed in subsequent patterning (i.e. exposure and developing) processes. In detail, a patterned photomask 600 is used to expose the dielectric portion 230 b to a light source (e.g. UV light source). The photomask 600 may have opaque portion which blocks and patterned transparent portions which allows light to pass through, as seen in arrows of FIG. 20 .

After the exposure, the exposed portions of the dielectric portion 230 b is chemically altered and may be removed by use of developing solution. After removal of exposed portion, a patterned dielectric portion 230 b with openings 236 a and openings 236 b are formed, as shown in FIG. 21 . Openings 236 a expose the portions of dielectric portion where opening 234 are formed, thus exposing the conductive pillar TV and the semiconductor die 110 and the semiconductor die 120. Openings 236 b exposes the portions of the dielectric portion 230 a. In some embodiments, openings 236 b correspond to trenches that extends along the top surface of the dielectric portion 230 a.

In FIG. 22 , a seed layer SL2 is formed on the patterned dielectric portion 230 a, exposed portions of the dielectric portion 230 a and the exposed portions of the conductive pillar TV and the semiconductor dies 110 and 120. That is, the seed layer SL2 is formed on the dielectric portion 230 b and conformal to the shape of the openings 236 a and openings 236 b. The seed layer SL2 may be formed using, for example PVD or the like. The PVD may be sputtering. In some embodiments, the seed layer SL2 is a metal layer, which may be a single layer or a composite layer comprising sub-layers formed of different materials. In some embodiments, the seed layer SL2 includes a titanium layer and a copper layer over the titanium layer.

Referring to FIG. 23 , a conductive material 234 is then formed over the seed layer filling the openings 236 a and the openings 236 b. In some embodiments, the conductive material may be formed by plating, such as electroplating, electroless plating, or the like. The conductive material may be a metal such as copper, titanium, tungsten, aluminum, or the like. The conductive material is formed to a level that is above the top surface of the seed layer SL2 disposed thereunder.

Referring to FIG. 24 , the conductive material 234, seed layer SL2 and dielectric portion 230 b are partially removed and planarized to define the conductive features 238 a and conductive features 238 b. That is, the excess portion of the conductive materials 234 and the seed layer SL2 are removed. The partial removal and planarization process removes conductive material 234 and seed layer SL2 that are disposed above the top surface of the dielectric portion 230 b. Accordingly, any conductive material 234 and/or seed layer SL2 that electrically connects conductive material disposed in any two adjacent openings 236 a and openings 236 b are removed, leaving behind a substantially leveled top surface. In some embodiments, the partial removal and planarization of the conductive material 234, seed layer SL2 and dielectric portion 230 b may be performed by a grinding process and/or a planarization process such as a chemical mechanical polishing (CMP) process. In some embodiments, the thickness T3 of the dielectric portion 230 b after the planarization process may between about 0.2 µm to about 0.9 µm.

Still referring to FIG. 24 , the conductive features 238 a refer to the portion of conductive material embedded in the dielectric portion 230 a. That is, the conductive features 238 a are conductive vias which electrically connect the conductive pillar TV and the semiconductor dies 110 and 120 to the conductive features 238 b disposed above the conductive features 238 a. The conductive features 238 b refer to conductive features that is embedded in the dielectric portion 230 b. In a top view (not shown), the conductive features 238 b may be illustrated as fine pitched conductive traces that extends along the surface of the dielectric portion 230 a for increased routing density.

In some embodiments, the conductive features 238 a may have dimensions similar to the conductive features 138 a discussed above with reference to FIG. 9 . In some embodiments, the conductive features 238 b may have dimensions similar to the conductive features 138 b discussed above with reference to FIG. 9 . In some embodiments, the critical dimension of the conductive features 238 b is smaller than the critical dimension of the conductive features 238 a. In some embodiments, the critical dimension of the conductive features 238 a may be between about 1.0 µm to about 5.0 µm. In some embodiments, the critical dimension of the conductive features 238 b may be between about 0.2 µm to about 0.9 µm.

FIGS. 25 through 26 illustrates the formation of additional RDL 240 over the first RDL 230. The RDL 240 includes dielectric portion 240 a, dielectric portion 240 b, conductive features 248 a and conductive features 248 b. The materials used and the process of forming the RDL 240 may be the same as the process of forming RDL 230 illustrated in FIGS. 19 through 24 .

In some embodiments, the RDL 240 is a fine pitch RDL for high density routing having critical dimensions similar to the RDL 230. In other words, the dielectric portion 240 a may be similar to the dielectric portion 230 a, the dielectric portion 240 b may be similar to the dielectric portion, the conductive features 248 a may be conductive vias that is similar to conductive features 238 a, and the conductive features 248 b may be redistribution lines formed above conductive features 248 a that is similar to conductive features 238 b. In an alternative embodiment, the formation of the RDL 240 is omitted. That is, only one fine pitch RDL 230 is formed. In some other embodiment, more than one additional fine pith RDL 240 may be formed on the RDL 230. That is, the processes of FIGS. 19 through 24 may be repeatedly performed on RDL 230.

Due to the removal of excess conductive material 234 and planarization to form the conductive features 238 a and conductive features 238 b discussed above with reference to FIG. 24 , a surface with high DOP is provided for additional fine pitch RDL 240 to be formed thereon. The high DOP allows the RDL 240 to be formed with larger process window, thus increasing the yield rate of fine pitch packaging process. That is, due to the top surface of RDL 230 having good surface planarity, the dielectric portion 240 a and dielectric portion 240 b may be formed with high DOP thereon. Subsequent patterning (i.e. photolithography) process performed thereon may have good resolution, and fine pitch RDL 240 may be achieved.

Referring to FIGS. 27 through 29 , after the RDL 240 is formed, a large scaled RDL and conductive connectors 164 are formed. The large scaled RDL includes dielectric portion 250, dielectric portion 160, conductive features 154 and UBM 162. In FIG. 27 , a dielectric portion 250 is formed over the RDL 240. The top surface of the dielectric portion 250 may be substantially level due to the removal planarization of RDL 240. In some embodiments, the dielectric portion 250 is formed of a photosensitive dielectric material similar to the dielectric portion 150. The dielectric portion 250 may then be patterned to form opening exposing some conductive features 248 b. In FIG. 28 , conductive features 154 are formed in the patterned opening of dielectric portions 250 and on the top surface of the dielectric portion 250. In some embodiment, the conductive features 154 are formed with a seed layer as discussed above with reference to FIG. 14 . Here, the conductive features 154 collectively refer to the conductive features which connects conductive feature 248 b to the top surface of the dielectric portion 250 and conductive features which is above the dielectric portion 250 which performs redistribution function.

In FIG. 29 , a dielectric portion 160, an under-ball metallurgy (UBM) 162 and conductive connector 164 are formed with the similar material and method as discussed above with reference to FIG. 15 . The details of which are not repeated herein. Although not illustrated, after the formation of conductive connector 164, the package may be de-bonded from the carrier 100 and flipped over for subsequent bonding to a package 300 and singulation process, similar to the process described with reference to FIGS. 16 to 18 .

FIGS. 30 through 35 illustrate cross-sectional views of various processing steps during formation of a redistribution structure in accordance with some other embodiments. A single package region is illustrated in FIGS. 30 through 35 , but multiple package regions may be packaged simultaneously, constituting a wafer level packaging process.

Referring to FIGS. 30 through 33 , an RDL is formed over the semiconductor dies 110 and 120, the conductive pillars TV and the insulating encapsulant MC. As illustrated in FIG. 33 , the RDL includes a dielectric layer 330, conductive features 338 a and conductive features 338 b. Conductive features 338 a and conductive features 338 b are referred to as redistribution lines. In some embodiments, conductive features 338 a and conductive features 338 b are formed by a damascene process, more particularly, a dual damascene process, described in greater detail below. In some embodiments, the RDL is a fine pitch RDL having critical dimension less than 1.0 µm.

Referring to FIG. 30 , a package structure similar to FIG. 5 is provided. In FIG. 30 , a dielectric layer 330 is provided over the semiconductor dies 110 and 120, the conductive pillars TV and the insulating encapsulant MC. The dielectric layer 330 is formed of a positive tone photosensitive dielectric material such as PBO, polyimide, BCB, phenolic, acrylate, phenolic-epoxy hybrid, or the like. The dielectric layer 330 may be formed by any acceptable deposition process, such as spin coating, chemical vapor deposition (CVD), laminating, the like, or a combination thereof. The use of positive tone photosensitive dielectric material allows openings with smaller dimension to be formed in subsequent patterning (i.e. exposure and developing) processes.

Still referring to FIG. 30 , after forming the dielectric layer 330, the dielectric layer 330 is patterned by photolithography using a patterned photomask 600. The photomask 600 may have opaque portion which blocks and patterned transparent portions which allows light to pass through, as seen in arrows of FIG. 30 . During the exposure process including one or more exposure steps, two regions E1 and E2 of the dielectric layer are exposed to the patterned light. Referring to FIG. 30 , region E1 refers to the region with dashed lines which extends from the top surface of the dielectric layer 330 through to the bottom surface of the dielectric layer 330. Region E2 refers to the region with dashed lines which extends from the top surface of the dielectric layer 330 into dielectric layer 330 but not through to the bottom surface of the dielectric layer. Both regions correspond to individual tapered openings in the subsequent removal of the regions E1 and regions E2.

In some embodiments, when the exposure process is a two-step process, regions E1 may first be exposed to patterned light using a first photomask before exposing region E2 using a second photomask or vice versa. In some embodiment, the exposure to regions E1 and regions E2 may be performed simultaneously in a single step using a half-tone photomask. After the exposure, the exposed portions of the dielectric layer 330 is chemically altered and may be removed by use of developing solution. After removal of exposed portions, a patterned dielectric layer 330 with openings 336 a and openings 336 b are formed, as shown in FIG. 31 . Openings 336 a are vias exposing the conductive pillar TV, the semiconductor die 110 and the semiconductor die 120. Openings 336 b are recesses formed in the dielectric layer 330. In some embodiments, openings 336 b correspond to trenches that extends along the dielectric layer 330.

Referring to FIG. 32 , a seed layer is formed on the patterned dielectric layer 330, the exposed portions of the conductive pillar TV and the semiconductor dies 110 and 120. That is, a seed layer is formed on the dielectric portion 230 b and conformal to the shape of the openings 336 a and openings 336 b. In some embodiments, the seed layer is formed with the material and method similar to the seed layer SL2 discussed above with reference to FIG. 22 . After forming seed layer, a conductive material 334 is then formed over the seed layer filling the openings 336 a and the openings 336 b to a level that is above the top surface of the seed layer disposed thereunder. In some embodiments, the conductive material 334 is formed with the material and method similar to the conductive material 234 discussed above with reference to FIG. 23 .

Referring to FIG. 33 , the conductive material 334, seed layer and dielectric layer 330 are partially removed and planarized to define the conductive features 338 a and conductive features 338 b. That is, the excess portion of the conductive materials 334 and the seed layer are removed. The partial removal and planarization process removes conductive material 334 and seed layer that are disposed above the top surface of the dielectric layer 330 similar to the removal of conductive material 234 discussed above with reference to FIG. 24 . Accordingly, a substantially leveled top surface is formed. In some embodiments, the thickness T4 of the dielectric layer 330 after the planarization process may be between about 1.2 µm to about 5.9 µm.

Still referring to FIG. 33 , the conductive features 338 a refer to the portion of conductive material extending from the bottom surface of the dielectric layer 330 to the level of the bottom surface of opening 336 b (shown in FIG. 31 ). That is, the conductive features 338 a are conductive vias which electrically connect the conductive pillar TV and the semiconductor dies 110 and 120 to the conductive features 338 b disposed above the conductive features 338 a. The conductive features 338 b refer to conductive features that formed in openings corresponding to region E2. In a top view (not shown), the conductive features 338 b may be illustrated as fine pitched conductive traces that extends along the surface of the dielectric layer 330 for increased routing density.

In some embodiments, the conductive features 338 a may have dimensions similar to the conductive features 138 a discussed above with reference to FIG. 9 . In some embodiments, the conductive features 338 b may have dimensions similar to the conductive features 138 b discussed above with reference to FIG. 9 . In some embodiments, the critical dimension of the conductive features 338 b is smaller than the critical dimension of the conductive features 338 a. In some embodiments, the critical dimension of the conductive features 338 a may be between about 1.0 µm to about 5.0 µm. In some embodiments, the critical dimension of the conductive features 338 b may be between about 0.2 µm to about 0.9 µm.

FIG. 34 illustrates the formation of additional RDL similar to the RDL discussed with reference to FIGS. 30 through 32 . The additional RDL includes dielectric layer 340 and conductive material 344. The materials used and the process of forming the dielectric layer and conductive material 344 may be the same as the process illustrated in FIGS. 30 through 32 .

Referring to FIG. 35 , excess portion of the conductive material 344 is removed and planarization is performed on the dielectric layer 340. After planarization process, dielectric layer 340 include conductive features embedded therein. The conductive features embedded in dielectric layer 340 correspond to fine pitch redistribution lines similar to that of the conductive features 338 a and conductive features 338 b. In an alternative embodiment, formation of additional RDL including the dielectric layer 340 and the conductive features embedded therein may be omitted. That is, only one fine pitch RDL is formed. In some other embodiment, more than one additional fine pith RDL may be formed. That is, the processes of FIGS. 30 through 33 may be repeatedly performed to form multiple fine pitch RDLs.

Still referring to FIG. 35 , after the fine pitch RDL is formed, a large scaled RDL and conductive connectors 164 are formed. The large scaled RDL includes dielectric portion 250, dielectric portion 160, conductive features 154 and UBM 162. The large scaled RDL may be formed by materials and methods as discussed above with reference to FIGS. 27 through 29 . The details of which are not repeated herein. Although not illustrated, after the formation of conductive connector 164, the package may be de-bonded from the carrier 100 and flipped over for subsequent bonding to a package 300 and singulation process, similar to the process described with reference to FIGS. 16 to 18 .

In the above-mentioned embodiments, a chip package having a fine pitch RDL for high routing density is provided. To reduce critical dimension of the fine pitch RDL, a surface with high degree of planarization (DOP) is provided for the formation every fine-pitch RDL. By providing high DOP surface, the process window of manufacturing fine pitch RDL may be increased, thereby increasing the yield rate of the package structures having at least one fine pitch RDL. Furthermore, the conductive features in the fine-pitch RDLs are formed by using the damascene (e.g. single damascene or dual damascene) process, allowing fine pitch to be achieved. Moreover, openings (e.g. trenches) defining the conductive features having fine line width or fine line spacing may be patterned on high resolution photoresists or positive-tone photosensitive dielectric layer to effectively decrease the critical dimension.

In accordance with some embodiments of the present disclosure, a chip package including a semiconductor die, an insulating encapsulant encapsulating the semiconductor die; and a first redistribution layer over the semiconductor die and the encapsulant is provided. The first redistribution includes a first redistribution portion and a second redistribution portion in contact with the first redistribution portion, the first redistribution portion being between the second redistribution portion and the semiconductor die, wherein the first redistribution portion includes a first dielectric portion and a plurality of first conductive features embedded in the first dielectric portion, the plurality of first conductive features electrically connecting the semiconductor die to the second redistribution portion, the second redistribution portion includes a second dielectric portion and a plurality of second conductive features embedded in the second dielectric portion and connected to the first conductive features, a top surface of the second dielectric portion is substantially level with top surfaces of the plurality of second conductive features.

In accordance with alternative embodiments of the present disclosure, a method for forming a chip package is provided. The method includes the following steps. Laterally encapsulating a semiconductor die with an insulating encapsulant; forming a first dielectric portion over the insulating encapsulant and the semiconductor die, the first dielectric portion comprising a plurality of via holes, forming a second dielectric portion over the first dielectric portion; and forming a plurality of first conductive features in the plurality of via holes and a plurality of second conductive features connected to the plurality of first conductive features, wherein the plurality of second conductive features are embedded in the second dielectric portion, and a top surface of the second dielectric portion is substantially level with top surfaces of the plurality of second conductive features.

In accordance with yet alternative embodiments of the present disclosure, another method of forming a chip package is provided. The method includes the following steps. Laterally encapsulating a semiconductor die with an insulating encapsulant, forming a redistribution layer, wherein forming the redistribution layer includes: forming a first dielectric layer over the insulating encapsulant and the semiconductor die, the first dielectric layer comprising a plurality of via holes and a plurality of trenches above the via holes, and forming a plurality of first conductive features in the via holes and a plurality of second conductive features in the trenches, wherein a top surface of the first dielectric layer is substantially level with top surfaces of the plurality of second conductive features.

The foregoing outlines features of several embodiments so that those skilled in the art may better understand the aspects of the present disclosure. Those skilled in the art should appreciate that they may readily use the present disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and that they may make various changes, substitutions, and alterations herein without departing from the spirit and scope of the present disclosure. 

What is claimed is:
 1. A redistribution structure, comprising: stacked dielectric portions; conductive features embedded in the stacked dielectric portion, the conductive features comprising: at least one first conductive feature, comprising a first via portion, a first wiring portion on the first via portion, and a first seed layer, wherein sidewalls and bottom surfaces of the first via portion and the first wiring portion are spaced apart from at least one first dielectric portion among the stacked dielectric portions by the first seed layer; a second conductive feature penetrating through a second dielectric portion among the stacked dielectric portions, the second conductive feature comprising a second via portion, a second wiring portion on the second via portion, and a second seed layer, wherein the second seed layer does not cover sidewalls of the third wiring portion; and a third conductive feature disposed on the second dielectric portion, the third conductive feature comprising a third wiring portion and a third seed layer, wherein the third wiring portion is spaced apart from the second dielectric portion by the third seed layer.
 2. The redistribution structure of claim 1, wherein at least one first conductive feature comprise a bottom tier conductive feature and a top tier conductive feature stacked on the bottom tier conductive feature.
 3. The redistribution structure of claim 2, wherein the second conductive feature is disposed on and electrically connected to the top tier conductive feature.
 4. The redistribution structure of claim 1, wherein the second conductive feature is disposed over and electrically connected to the at least one first conductive feature.
 5. The redistribution structure of claim 1, wherein the second dielectric portion is disposed on the at least one first dielectric portion, and the second conductive feature is partially embedded in the second dielectric portion.
 6. The redistribution structure of claim 1, wherein the second dielectric portion is spaced apart from the second via portion and the second wiring portion by the second seed layer.
 7. The redistribution structure of claim 1, wherein the second dielectric portion is spaced apart from the third wiring portion by the third seed layer.
 8. The redistribution structure of claim 1, wherein the third conductive feature and the second wiring portion are disposed at a same level height, and the third conductive feature is spaced apart from the at least one first conductive feature by the second dielectric portion.
 9. A redistribution structure, comprising: stacked dielectric portions; conductive features embedded in the stacked dielectric portion, the conductive features comprising: at least one first conductive feature, comprising a first via portion, a first wiring portion on the first via portion, and a first seed layer, wherein sidewalls and bottom surfaces of the first via portion and the first wiring portion are spaced apart from at least one first dielectric portion among the stacked dielectric portions by the first seed layer; a second conductive feature penetrating through a second dielectric portion among the stacked dielectric portions, the second conductive feature comprising a second via portion, a second wiring portion on the second via portion, and a second seed layer, wherein the second seed layer does not cover sidewalls of the third wiring portion; and a third conductive feature, comprising a third wiring portion and a third seed layer, wherein the third seed layer covers sidewalls and a bottom surface of the third wiring portion.
 10. The redistribution structure of claim 9, wherein at least one first conductive feature comprise a bottom tier conductive feature and a top tier conductive feature stacked on the bottom tier conductive feature.
 11. The redistribution structure of claim 10, wherein the second conductive feature is disposed on and electrically connected to the top tier conductive feature.
 12. The redistribution structure of claim 9, wherein the second conductive feature is disposed over and electrically connected to the at least one first conductive feature.
 13. The redistribution structure of claim 9, wherein the second dielectric portion is disposed on the at least one first dielectric portion, and the second conductive feature is partially embedded in the second dielectric portion.
 14. The redistribution structure of claim 9, wherein the second dielectric portion is spaced apart from the second via portion and the second wiring portion by the second seed layer.
 15. The redistribution structure of claim 9, wherein the third conductive feature is embedded in the at least one first dielectric portion.
 16. The redistribution structure of claim 9, wherein the third conductive feature and the first wiring portion are disposed at a same level height.
 17. A redistribution structure, comprising: a first dielectric portion; a first group of conductive features embedded in the first dielectric portion, the first group of conductive features comprising: a first conductive feature, comprising a first via portion, a first wiring portion on the first via portion, and a first seed layer, wherein the first seed layer covers sidewalls and bottom surfaces of the first via portion and the first wiring portion; a second conductive feature, comprising a second wiring portion and a second seed layer, wherein the second seed layer covers sidewalls and a bottom surface of the second wiring portion; a second dielectric portion; a second group of conductive features disposed on the second dielectric portion, the second group of conductive features comprising: a third conductive feature penetrating through the second dielectric portion, the third conductive feature comprising a third via portion, a third wiring portion on the third via portion, and a third seed layer, wherein the third seed layer does not cover sidewalls of the third wiring portion; and a fourth conductive feature disposed on a top surface of the second dielectric portion, the fourth conductive feature comprising a fourth wiring portion and a fourth seed layer, wherein the fourth seed layer does not cover sidewalls of the fourth wiring portion.
 18. The redistribution structure of claim 17, wherein the second conductive feature is embedded in the at least one first dielectric portion, and the second conductive feature and the first wiring portion are disposed at a same level height.
 19. The redistribution structure of claim 17, wherein the fourth conductive feature and the third wiring portion are disposed at a same level height.
 20. The redistribution structure of claim 17, wherein the second dielectric portion is spaced apart from the third via portion and the third wiring portion by the third seed layer, and the second dielectric portion is spaced apart from the fourth wiring portion by the fourth seed layer. 